如何使用CoreText替换Swift中的UILabel？

目前我正在使用UILabel在屏幕上显示文本：

var label = UILabel() view.addSubView(label) label.backgroundColor = UIColor.whiteColor() label.numberOfLines = 2 label.font = UIFont.systemFontOfSize(20, weight: UIFontWeightMedium) label.frame = CGRectMake(0, 0, 100, 50) label.text = "Hi, this is some text..." 

如何在Swift中使用CoreText替换上面的内容？

Answer 1

以下代码解决了我的问题：

 override func drawRect(rect: CGRect) { super.drawRect(rect) let context = UIGraphicsGetCurrentContext() // Flip the coordinate system CGContextSetTextMatrix(context, CGAffineTransformIdentity); CGContextTranslateCTM(context, 0, self.bounds.size.height); CGContextScaleCTM(context, 1.0, -1.0); let path = CGPathCreateMutable() CGPathAddRect(path, nil, self.bounds) let str = NSMutableAttributedString(string: "some text goes here...") // set font color str.addAttribute(kCTForegroundColorAttributeName as String, value:UIColor.blackColor() , range: NSMakeRange(0,str.length)) // set font name & size let fontRef = UIFont.systemFontOfSize(20, weight: UIFontWeightMedium) str.addAttribute(kCTFontAttributeName as String, value: fontRef, range:NSMakeRange(0, str.length)) let frameSetter = CTFramesetterCreateWithAttributedString(str) let ctFrame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0,str.length), path, nil) CTFrameDraw(ctFrame, context!) } 

Answer 2

Swift 4.0的更新：

 override func draw(_ rect: CGRect) { super.draw(rect) // context allows you to manipulate the drawing context (i'm setup to draw or bail out) guard let context: CGContext = UIGraphicsGetCurrentContext() else { return } // Flip the coordinate system context.textMatrix = CGAffineTransform.identity; context.translateBy(x: 0, y: self.bounds.size.height); context.scaleBy(x: 1.0, y: -1.0); let path = CGMutablePath() path.addRect(self.bounds) let str = NSMutableAttributedString(string: "00:00:00") // set font color str.addAttribute(NSAttributedStringKey(rawValue: kCTForegroundColorAttributeName as String), value:UIColor.purple , range: NSMakeRange(0,str.length)) // set font name & size let fontRef = UIFont.systemFont(ofSize: 20, weight: UIFont.Weight.bold) str.addAttribute(NSAttributedStringKey(rawValue: kCTFontAttributeName as String), value: fontRef, range:NSMakeRange(0, str.length)) let frameSetter = CTFramesetterCreateWithAttributedString(str) let ctFrame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0,str.length), path, nil) CTFrameDraw(ctFrame, context) } 

Answer 3

尝试这个：

 func drawText(context: CGContextRef, text: NSString, attributes: [String: AnyObject], x: CGFloat, y: CGFloat) -> CGSize { let font = attributes[NSFontAttributeName] as UIFont let attributedString = NSAttributedString(string: text, attributes: attributes) let textSize = text.sizeWithAttributes(attributes) // y: Add font.descender (its a negative value) to align the text at the baseline let textPath = CGPathCreateWithRect(CGRect(x: x, y: y + font.descender, width: ceil(textSize.width), height: ceil(textSize.height)), nil) let frameSetter = CTFramesetterCreateWithAttributedString(attributedString) let frame = CTFramesetterCreateFrame(frameSetter, CFRange(location: 0, length: attributedString.length), textPath, nil) CTFrameDraw(frame, context) return textSize } 

并且这样打电话：

 var textAttributes: [String: AnyObject] = [ NSForegroundColorAttributeName : UIColor(white: 1.0, alpha: 1.0).CGColor, NSFontAttributeName : UIFont.systemFontOfSize(17) ] drawText(ctx, text: "Hello, World!", attributes: textAttributes, x: 50, y: 50) 

希望这个有效！

Answer 4

针对swift 3.0进行了更新：

 if let context = UIGraphicsGetCurrentContext(){ // Flip the coordinate system context.textMatrix = CGAffineTransform.identity; context.translateBy(x: 0, y: self.bounds.size.height); context.scaleBy(x: 1.0, y: -1.0); let path = CGMutablePath() path.addRect(self.bounds) let str = NSMutableAttributedString(string: "some text goes here...") // set font color str.addAttribute(kCTForegroundColorAttributeName as String, value:UIColor.black , range: NSMakeRange(0,str.length)) // set font name & size let fontRef = UIFont.systemFont(ofSize: 20, weight: UIFontWeightMedium) str.addAttribute(kCTFontAttributeName as String, value: fontRef, range:NSMakeRange(0, str.length)) let frameSetter = CTFramesetterCreateWithAttributedString(str) let ctFrame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0,str.length), path, nil) CTFrameDraw(ctFrame, context) }